Seawater desalination: the solution?
Water is an increasingly scarce commodity in many parts of the world, and it seems seawater desalination is one of very attractive solutions available to these regions. Of all the Earth’s water, 94 percent is saltwater from the oceans and only 6% is fresh. If plenty and easily accessible seawater could turn into fresh drinking water—what a miracle it would be for all the parched areas of the world. Desalination-of-seawater technology: where do we stand and what are the challenges or problems? I will briefly review the case of Western Australia and California and leave this question to be answered and discussed by more people.
Australia, one of the countries facing water crises, has advanced seawater-desalination technology. (The summar report of desalination technology in Australia seems to be very informative). Even though rainfall levels in Western Australia have been halved in recent decades, the area has been successfully fighting the water crisis by efforts to curb consumption and find new sources of freshwater—including from seawater desalination. The city of Perth, for instance, has opted to spend its way out of a water crisis by building a desalination plant. The second plant is to open in two years time—when a third of the state’s drinking supplies will come from treated seawater. Sydney, the largest city in Australia, is also building a desalination plant. The Sydney desalination plant is planned to supply up to 250 million liters of water a day, which is up to 15 per cent of Sydney’s water needs.
However, the skeptics point out the other side of this technology: desalination is not energy-efficient yet. Seawater desalination is inherently energy-intensive, and it takes more electricity to desalinate water at the new facility than to import it from elsewhere. For example, San Diego Gas & Electric will produce 97,165 metric tons of carbon dioxide annually to supply the Carlsbad desalination plant with the 274,400 MWh of electricity—the amount of electricity to produce 50 million gallons of drinking water each day for a year. By comparison, pumping the same volume from the north requires 112,005 MWh; and pumping it from the Colorado River Aqueduct, San Diego’s secondary source of water, requires 167,900 MWh each year, according to the Natural Resources Defense Council.